Ecological dynamics
Natural fertility, presence of shade, proximity to water, and nutritious forage make this site a preferred grazing area. The wet nature of the site protects it from grazing at times, but during dry conditions it is often the first site to be overused. Virginia wildrye (Elymus virginicus), eastern gamagrass (Tripsacum dactyloides), switchcane (Arundinaria gigantea), switchgrass (Panicum virgatum), and sedges (Carex spp.) decrease in abundance and are replaced by dallisgrass (Paspalum dilatatum), common Bermudagrass (Cynodon dactylon), and carpetgrass (Axonopus fissifolius) as abusive grazing continues. Shrubs and hardwood saplings invade the site in the absence of proper grazing management and brush management. Prolonged mismanagement or abandonment allows the site to become a hardwood forest dominated by water oak (Quercus nigra), willow oak (Quercus phellos), overcup oak (Quercus lyrata), and cedar elm (Ulmus crassifolia) on non-calcareous sites or green ash (Fraxinus pennsylvanica), eastern cottonwood (Populus deltoides), pecan (Carya illinoinensis), cedar elm, and sugarberry (Celtis laevigata) on calcareous sites.
State 1
Savannah
Two communities exist in the Savannah State: the 1.1 Wildrye/Sedge Savannah Community and the 1.2 Shrub Community. Community 1.1 is characterized by tall and midgrass dominating the understory, with 20 percent woody cover by ash and elm. Community 1.2 is characterized by a an increase in shade tolerant grasses and 20 to 40 percent canopy cover of woody species.
Community 1.1
Wildrye/Sedge Savannah
The reference plant community of this site is a savannah. Oak, elm, hackberry (Celtis spp.), cottonwood, ash, black willow (Salix nigra), pecan, and other large trees provide about a 20 percent canopy. The overstory canopy is denser immediately adjacent to the watercourse. The understory includes hawthorn (Crataegus spp.), greenbriar (Smilax spp.), rattan (Calamus spp.), peppervine (Ampelopsis arborea), grape (Vitis spp.), and trumpet creeper (Campsis radicans). Sedges, Virginia wildrye, switchcane, broadleaf woodoats (Chasmanthium latifolium), and rustyseed paspalum (Paspalum langei) are in shaded and wet areas and dominate the herbaceous plant community. Various combinations of beaked panicum (Panicum anceps), switchgrass, Indiangrass, big bluestem (Andropogon gerardii), little bluestem (Schizachyrium scoparium), eastern gamagrass, vinemesquite (Panicum obtusum), and Florida paspalum (Paspalum floridanum) may dominate drier, open areas.
Continuous yearlong grazing with no weed or brush management or abandoning the site for several years will tend to move towards a shrub-sapling community. Once woody shrubs and saplings invade the site, brush management in some form must be used to move back toward the savannah state. Prescribed burning is not a viable management tool on this site.
Community 1.2
Shrub
This plant community is a transitional community between the Savannah and Woodland State. It develops in the absence of proper grazing management and mechanical or chemical brush control treatments. It is usually the result of abandonment following cropping or yearly continuous grazing. Trees and shrubs begin to replace the grassland component of the savannah community. In addition to the naturally occurring cedar elm, water oak, hackberry, pecan, cottonwood, and green ash - honey locust (Gleditsia triacanthos), Chinese tallow (Triadica sebifera), and eastern persimmon (Diospyros virginiana) increase in density and canopy coverage (20 to 40 percent). Species whose seeds are windblown (elm, cottonwood, ash) or animal dispersed (persimmon, pecan, Chinese tallow) are the first to colonize and dominate the site.
Remnants of Virginia wildrye and eastern gamagrass may still occur but the herbaceous component of the community becomes dominated by lesser producing grasses and forbs. Shade-tolerant species such as broadleaf woodoats, longleaf woodoats (Chasmanthium sessiliflorum), Cherokee sedge (Carex cherokeensis), ironweed (Veronia baldwinii), buttercup (Ranunculus spp.), and goldenrod (Solidago spp.) are the most abundant species as canopy cover increases. Prescribed burning is not a viable option for returning this community to a savannah due to the moisture content in and lack of quantity of herbaceous fine fuels. Mechanical or chemical brush control as well as prescribed grazing must be applied to move this vegetative state back towards the reference plant community.
Pathway 1.1A
Community 1.1 to 1.2
The Wildrye/Sedge Savannah will transition to the Shrubland Community when continued heavy grazing pressure, no brush management, and/or field abandonment continues. The transition is evident when woody species canopy cover exceeds 20 percent and grasses shift composition to more shade-tolerant species.
Pathway 1.2A
Community 1.2 to 1.1
Restoration back to the Wildrye/Sedge Community requires brush management and prescribed grazing. Mechanical or chemical controls can be used to remove the woody species and shrubs. Prescribed grazing may require destocking and/or deferment.
State 2
Woodland
One community exists in the Woodland State, the Ash/Elm Woodland Community. It is characterized by shade tolerant grasses and an overstory canopy of 40 to 80 percent.
Community 2.1
Ash/Elm Woodland
This plant community is a closed overstory (40 to 80 percent) woodland dominated by green ash, cedar elm, overcup oak, water oak, willow oak, pecan, cottonwood, sycamore (Plantanus occidentalis), and black willow. Understory shrubs and sub-shrubs include yaupon, farkleberry (Vaccinium arboreum), possumhaw (Ilex decidua), American beautyberry (Callicarpa americana), and hawthorn. Woody vines also occur and include Alabama supplejack (Berchemia scandens), poison ivy (Toxicodendron radicans), grape, greenbrier, trumpet creeper, Virginia creeper (Parthenocissus quinquefolia), and peppervine.
A herbaceous understory is almost nonexistent but shade tolerant species including longleaf uniola, broadleaf woodoats, sedges, ironweed, ice plant (Verbesina lindheimeri), switchcane, eastern gamagrass, and goldenrod may occur in small amounts. Prescribed fire is not a viable treatment option for conversion of this site back to a semblance of the Wildrye/Sedge Savannah. Broadcast chemical brush control is not a treatment option either, however, individual plant treatment with herbicides on small acreages may be a viable option. Mechanical treatment of this site, along with seeding, is the most viable treatment option although probably not economical.
State 3
Invasion
One community exists in the Invasion State, the Bermudagrass/Dallisgrass Community. It is characterized by an invasion by tame pasture grasses. The invasive species may have been planted for agriculture purposes or they may have invaded from nearby pastures.
Community 3.1
Bermudagrass/Dallisgrass
The herbaceous community is dominated by common Bermudagrass, dallisgrass, carpetgrass, giant ragweed, and annual sumpweed. White clover (Trifloium repens), vetch (Vicia sativa), and annual ryegrass (Lolium multiflorum) may also occur. This community develops from years of heavy continuous grazing. Prescribed grazing may shift this community back towards the Wildrye/Sedge Savannah Community, but total restoration may not be possible as invasive species are hard to control.
State 4
Converted Land
The Converted Land State contains one community, the 4.1 Converted Land Community. The state is characterized by the land manager farming crops or planted grasses.
Community 4.1
Converted Land
Conversion of this site to cropland (primarily cotton) occurred from the middle 1800's to the early 1900's. Some remains in cropland today, typically cotton (Gossypium spp.), corn (Zea mays), sorghum (Sorghum spp.), and soybeans (Glycine max). Ditching, land leveling, and levee construction has significantly changed the topography and hydrology on many acres of this site. While restoration of this site to a semblance of the reference plant community is possible with seeding and prescribed grazing, complete restoration of the reference community in a reasonable time is very unlikely.
Following crop production, this site is often planted to native or introduced grasses and legumes for livestock grazing or hay production. Typical species planted include improved Bermudagrass varieties, bahiagrass, switchgrass, dallisgrass, eastern gamagrass, annual ryegrass (Lolium multiflorum), and white clover. Many of the introduced species (bahiagrass, Bermudagrass, and dallisgrass) are invasive - moving by wind, water, and animals. Once established, they are extremely difficult to remove and will hinder the reestablishment of native species. The establishment and maintenance of these species requires cultivation, fertilization, weed control, and prescribed grazing management.
Transition T1A
State 1 to 2
The Savannah State will transition to the Woodland State when continued heavy grazing pressure, no brush management, and/or field abandonment continues. The transition is evident when woody species canopy cover exceeds 40 percent and grasses shift composition to more shade-tolerant species.
Transition T1B
State 1 to 3
The Savannah State will transition to the Invasion State when continuous, yearlong heavy grazing occurs, coupled with the invasion of species like Bermudagrass and Dallisgrass.
Transition T1C
State 1 to 4
The transition to the Converted State occurs when the site is plowed for planting crops or pasture. The driver for the transition is the land manager's decision to farm the site.
Restoration pathway R2A
State 2 to 1
Restoration back to the Savannah State requires substantial energy inputs. Brush management and prescribed grazing will be needed to shift the community back to the reference state. Mechanical or chemical controls can be used to remove the woody overstory species back below 20 percent. Prescribed grazing may require destocking and/or deferment to manage the understory grasses back to those found in the reference community.
Transition T2A
State 2 to 3
The Woodland State will transition to the Invasion State when invasion by species like Bermudagrass and Dallisgrass occur. These species will invade from nearby pastures and compete with native vegetation.
Transition T2B
State 2 to 4
The transition to the Converted State occurs when the site is plowed for planting crops or pasture. The driver for the transition is the land manager's decision to farm the site.
Restoration pathway R3A
State 3 to 1
Restoration back to the Savannah State requires substantial energy inputs. If woody species are present, chemical or mechanical brush management will be required. Range planting may be required if invasive species have taken over completely. Total restoration back to the reference community may not be possible due to the challenge of completely removing invasive species from the community.
Transition T3A
State 3 to 4
The transition to the Converted State occurs when the site is plowed for planting crops or pasture. The driver for the transition is the land manager's decision to farm the site.
Restoration pathway R4A
State 4 to 1
The restoration to State 1 can occur when the land manager ceases agronomic practices. Range planting of native species found in the reference community will be required to bring back a similar community as the State 1 plant composition. The extent of previous soil disturbances will determine how much seedbed preparation will be needed, as well as the ability to be restored. Proper grazing and brush management will be required to ensure success.
Transition T4A
State 4 to 3
The Converted Land State will transition to the Invasion State when continued heavy grazing pressure, no brush management, and/or field abandonment occurs. The transition is evident when forbs, shrubs, and woody species begin to limit the production of planted crops or pasture grasses.
